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ECE Objective Questions { Microwave Devices and Circuits }

127. When the peak power is 10,00,000 watts and the average power is 800 watts then the duty cycle is
A. 0.008 per cent
B. 0.08 per cent
C. 0.8 per cent
D. 8 per cent

128. Which of the following method should be used for measurement of high values of VSWR?
A. single minima method
B. double minima method
C. either of the above
D. none of the above

129. For a rectangular waveguide having, having a as broader dimension and b as narrow dimension, the cut off wavelength for TElo will be
A. a
B. b
C. 2 a
D. 2 b

130.  The cavity magnetron uses strapping to
A. prevent mode jumping
B. prevent cathode back heating
C. ensure bunching
D. improve the phase-focusing effect

131. Waveguides are not feasible at low frequencies because the circuit dimensions are
A. small compared to a wavelength
B. large compared to a wavelength
C.both (a) and(b)
D. none of the above

132. Which diode does not use negative resistance for its operation
A. Backward
B. Gunn
D. Tunnel

133. A magnetic field is used in the cavity magnetron to
A. ensure that the oscillations are pulsed
B. prevent anode current in the absenceof oscillations
C. ensure that the electrons will orbit around the cathode
D. help in focusing the electron beam, thus preventing spreading.

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